With respect to sterilization of medical instruments, sterilization means a higher level treatment, differently from cleaning or disinfection, which refers to the complete elimination of all living microorganisms through physical or chemical action. At present, sterilization of medical instruments is carried out using ethylene oxide (EO) gas, steam, hydrogen peroxide, plasma, and so forth.
Recently, a new type of EO sterilizer which uses 100% EO gas and does no use CFC (chlorofluorocarbon) as carrier gas has emerged. However, as well known in the related art, EO gas is highly explosive. It is also reported that EO acts as genetically toxic substance resulting in mutations. In this regard, the American Conference of Governmental Industrial Hygienist (ACGIH) regulates the level of EO gas in working environments to be not greater than 1 ppm, and considers EO gas as potential carcinogen. However, with the new-type EO sterilizer, it is not easy to thoroughly control the level of EO gas below the allowed standard. Further, although the sterilization time was reduced, the sterilization time of the new-type EO sterilizer is still long at 3 to 5 hours.
Meanwhile, steam sterilization is evaluated as one of those methods that can satisfy a sterilization efficiency of a predetermined level and is safe. Steam sterilization is advantageous in that it is without toxicity, requires relatively low cost, and enables fast sterilization. However, a steam sterilizer can be used only for the medical instruments which are without problem when exposed to high humidity and temperature.
Also, a combination of hydrogen peroxide, ozone and plasma for sterilization is known in the related art. For example, a method of providing hydrogen peroxide in a sterilization chamber and generating plasma inside the sterilization chamber; a method of providing plasma and a steriliant simultaneously in a sterilization chamber; a method of providing oxygen in a sterilization chamber and transferring it to ozone by generating plasma; and a method of providing hydrogen peroxide along with ozone in a sterilization chamber; and so forth are known.
Further, a method of providing vaporized hydrogen peroxide in a sterilization chamber, followed by providing ozone to sterilize a sterilization subject, discharging gas out of the chamber, and decomposing hydrogen peroxide and ozone remaining near the sterilization subject by the plasma generated in the chamber is known in the art.
However, because the conventional sterilization apparatuses utilizing hydrogen peroxide, ozone and plasma are associated with a sterilization occurring at low, i.e., atmospheric, pressure, they provide relatively lower sterilization efficiency than the high-pressure apparatuses. Further, once sterilization begins, the air particles existing before the beginning of the sterilization interfere with the action of the steriliant, thereby decreasing sterilization efficiency. Besides, the fact that an expensive plasma apparatus is required to generate plasma in the sterilization chamber remains an obstacle in the wide spread of sterilization apparatuses in the medical field.